The ventilation of drives exceeding 50 m length to be such as to dilute the nitrous fumes produced by blasting to . . . . . . . . and CO to . . . . . . . . within a period of . . . . . . . . min in long tunnel.
A. 5 ppm, 50 ppm, 5
B. 1 ppm, 25 ppm, 10
C. 10 ppm, 40 ppm, 2
D. 5 ppm, 40 ppm, 5
Answer: Option A
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